What does ULPA’s MPPS mean?

MPPS is the abbreviation of Most Penetrating Particle Size, which is usually called the most penetrating particle size in Chinese.

It means: under the specified test conditions, there is a particle size range in which particles can relatively easily penetrate the filter material. The particle size corresponding to this interval is MPPS.

It's not some fixed number. Many people think that MPPS is 0.12 microns or 0.3 microns, which is not accurate. The specific value of MPPS is related to the type of filter material, air flow speed, and detection method. The MPPS of different products may be different, and the same product may also change under different test conditions. Therefore, judging the performance of a ULPA depends on how it measures the MPPS efficiency, rather than applying a fixed particle size.

Why is there the easiest particle size to penetrate?

Behind this is the result of the joint action of several filtration mechanisms.

Larger particles are mainly captured by interception and inertial collision. The larger the particles, the easier they hit the fibers.

Very small particles undergo Brownian motion. They collide with fibers and are adsorbed during random motion. The diffusion effect is obvious and the efficiency is high.

Particles in between are not strong enough in interception and diffusion, and are relatively easy to penetrate. This range of particle size is the range where MPPS is located.

Therefore, the change of filtration efficiency with particle size is not monotonic. It is not that the smaller it is, the harder it is to filter, nor that the bigger it is, the easier it is to filter. Near MPPS, the efficiency reaches a relatively low point. ULPA's grade evaluation is measured under the most unfavorable particle size conditions - using the most difficult particles to evaluate can reflect the true capabilities of the product.

What are the conditions required to test MPPS?

MPPS is not a value that can be 'seen' directly. It measures the penetration rate under different particle sizes and then finds the interval with higher penetration rate.

Test methods should be implemented in accordance with applicable standards. Different standards may have different requirements for aerosols, measuring instruments and data processing.

The test air volume should be clear. The airflow speed affects the trajectory of particles in the filter material and also affects the position of the MPPS.

The test objects must be clear. Is it a filter material sample or a complete finished product? The filter material test reflects the material performance, and the impact of pleating, edge sealing and assembly on the finished product must also be considered. For specific differences, please refer to the instructions related to filter material grade and complete machine grade.

How to read the report

After getting a ULPA efficiency report, there are at least the following information related to MPPS:

MPPS particle size or interval. The report should state what MPPS was determined in the test, or within which range.

the corresponding efficiency value. What is the penetration rate or efficiency under this MPPS? This is the core data for level determination.

Test air volume. At what air volume is the efficiency measured? MPPS and efficiency may be different under different air volumes.

Test objects and standards. Is it filter material or finished product, which standard should be followed.

If the report only writes the efficiency of a fixed particle size and does not indicate whether it was measured under MPPS conditions, the data should be interpreted with caution. It may satisfy a certain project agreement, but may not be directly used for grade determination.

Practical implications in project judgment

The concept of MPPS mainly affects two things in actual projects:

Level check. Purchasing requirement U16, is the report provided by the supplier measured based on MPPS efficiency? Does the test method meet the contractually agreed standards? Only after these are confirmed can the grade judgment be based on.

Product comparison. Both products claim to be U16, but the MPPS efficiency of one is measured at low air volume, and the other is measured at design air volume. The two cannot be directly compared. It is necessary to unify the test conditions before looking at the data.

Verification after replacement. If a different brand or model of filter element is replaced, the MPPS efficiency test conditions may be different even if the grade is the same. On-site leak detection and area testing after replacement are necessary to confirm the actual effect. involving HEPA/ULPA air filter products of different grades have the same verification methods, and the criteria are implemented according to the corresponding standards. Supporting FFU fan filter unit or For the fan filter unit system at the EFU equipment end, the actual performance after installation must also be confirmed.

Project judgment example

Two fiberglass and PTFE ULPA products are both labeled U15, but have different MPPS efficiency data.

At this time we cannot simply say which one is better. First confirm whether the MPPS test conditions of the two products are comparable: whether the test air volume is the same, whether the test object is the filter material or the finished product, and whether the standards used are consistent. If conditions are different, data differences may come from test conditions rather than product performance.

After the conditions are aligned, the selection is made based on the resistance, installation space and system conditions. involving For specific products of ULPA ultra-high efficiency filters , MPPS efficiency data should come from the testing data of the corresponding model.

Selection and Acceptance Checklist

About Aili Industrial’s testing data cooperation

MPPS efficiency is the core data for grade determination. Whether the test conditions in the report are complete directly affects whether this data can be used.

Aili Industrial's manufacturing system covers filters, motors, fans, control systems and complete machine assembly, and can provide ULPA ultra-high efficiency filter and supporting air supply equipment. Testing data for the corresponding model can be provided according to the project agreement, and the filter and When the FFU fan filter unit and EFU are delivered together, the corresponding relationship between the whole machine test and the filter element test can be checked uniformly.

Clarifying the standard version, test requirements and report form when making an inquiry will help confirm the basis for grade determination. Specific performance is subject to the testing data of the corresponding model.